Using phase change expansion of a substance to perform work on a workpiece

ABSTRACT

Apparatus and method for working of a workpiece use the expansion of water in a container during the freezing process to drive a piston against a workpiece that is positioned to at least partially overlie a cross-sectional area of a hollow interior of the container. Use of a piston with a tapered working end focuses the resulting force against a small area of the workpiece in order to produce a bend in the workpiece at the point of application. In environments where conventional bending tools are not available, the apparatus can be used to perform bending or other operations on workpieces of varying materials.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. 119(a) of Canadian Patent Application Serial No. 2,747,897, filed Aug. 3, 2011.

FIELD OF THE INVENTION

The present invention relates generally to deriving mechanical work from expansion of a substance during a phase change, and more particularly to an apparatus and method for exploiting the phase change expansion to perform a working operation on a workpiece.

BACKGROUND OF THE INVENTION

When fresh water is cooled in a closed envelope, the internal pressure increases as ice is formed (phase change from water to ice). The resulting pressure reduces the freezing point below zero centigrade.

Due to the nature of the micro-structure of water, the volume of a specific weight of water increases when the water freezes to ice. The interspaces between molecules increase when water is transformed to ice. This increase of volume may be utilized as a mechanical work if well-directed.

It is possible to convert part of the energy of freezing to mechanical work. This work results from the increase of volume at freezing. The efficiency of the conversion of thermal energy to mechanical energy depends on the engineering design and structure of the used system.

Previous devices or systems for harnessing energy from the expansion of freezing water for various useful purposes are disclosed in U.S. Pat. Nos. 2,215,157, 6,332,318, 4,075,845, 4,220,006, 4,264,556, 5,375,983 and 4,186,558, French Patent Numbers 2676094 and 2833316 and “Prototype device for converting freezing energy into mechanical work” by Habeebullah, B, Zaki, G. M., & Akyurt, M. (Energy Conversion and Management, Volume 44, Issue 2, January 2003, pages 251-265).

Applicant has created a further contribution to the prior efforts in this field by developing a unique apparatus and method for exploiting the expansion of water as it changes state from liquid to solid in order to perform a bending or other working operation on a workpiece.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an apparatus for working of a workpiece, the apparatus comprising:

a container comprising a hollow interior space for receipt of a substance known to expand when transitioning from one phase to another;

a closure member for closing off a respective end of the hollow interior space of the container in a fluid-tight manner containing the substance within the hollow cylindrical interior space at said respective end.

a piston slidable within a cylindrical portion of the hollow interior space of the container along an axis of said hollow interior space;

a fluid-tight seal between the piston and a boundary wall closing around the axis of the hollow space for containing the substance within the hollow interior space between the piston and the closure member; and

a workpiece support feature arranged to support the workpiece in a position placing at least part of the workpiece over a cross-sectional area of the hollow interior space of the container.

According to a second aspect of the invention there is provided an apparatus for working of a workpiece, the apparatus comprising:

a container comprising a hollow interior space containing a substance known to expand when transitioning from one phase to another;

a closure member closing off a respective end of the hollow interior space of the container in a fluid-tight manner.

a piston slidably disposed within a cylindrical portion of the hollow interior space of the container;

a fluid-tight seal between the piston and a boundary wall closing around the axis of the hollow space to contain the substance within the hollow interior space between the fluid-tight seal and the closure member; and

a workpiece support feature arranged to support the workpiece in a position placing at least part of the workpiece over a cross-sectional area of the hollow interior space of the container.

Preferably the workpiece support feature comprises a workpiece passage extending into said container and passing through the hollow interior space thereof at a distance from the closure member for receipt of the workpiece in the passage in a position placing a part of the workpiece within the hollow interior of the container on a side of the piston opposite the closure member.

Preferably the workpiece passage comprises a cylindrical bore.

Preferably the closure member is removably engagable to the container for selective opening and closing of the respective end of the hollow interior space.

Preferably the closure member and the container are matingly threaded.

Preferably a working end of the piston comprises a non-planar surface for working the workpiece.

The working end of the piston may be at least partially conical. Alternatively, the working end of the piston may be wedge-shaped.

Preferably there is provided a cover for closing off a second end of the hollow interior space.

Preferably the cover is selectively engagable to and removable from the container.

The piston may be one of a plurality of differently shaped pistons selectable for use within the hollow interior, in which case each piston preferably comprises a peaked end tapering at a respectively different angle.

Preferably the substance is one that expands as it transitions into a solid state.

Preferably the substance is water.

According to a third aspect of the invention there is provided a method of working a workpiece, the method comprising:

(a) providing a container comprising a hollow interior space that has at least one closed end and contains a substance known to expand when transitioning from one phase to another;

(b) positioning the workpiece in a manner holding at least part of the workpiece over a cross-sectional area of the hollow interior space of the container; and

(c) with the substance contained between the closed end of the hollow interior space and a piston slidably disposed within a cylindrical portion of the hollow interior space, causing the substance to transition from the one phase to the other to force the piston against the workpiece to perform a working operation thereon.

Preferably step (c) comprises causing the substance to solidify.

Preferably step (c) comprises cooling the substance.

Preferably step (c) comprises freezing the substance.

Preferably forcing the piston against the workpiece in step (c) forms a bend in the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which illustrate exemplary embodiments of the present invention:

FIG. 1 is an exploded perspective view of an apparatus of the present invention for bending bar-shaped or rod-shaped workpieces using the expansion of water during the freezing process.

FIG. 2 is a schematic cross-sectional illustration of an apparatus like that of FIG. 1 in a prepared state ready for bending a rod-shaped workpiece.

FIG. 3 is a schematic cross-section illustration of the apparatus of FIG. 2 in a finished state after having bent the rod-shaped workpiece.

FIG. 4 shows 12 mm-diameter stainless steel rods bent by a test apparatus of the present invention.

FIG. 5 shows 6 mm-diameter copper rods that were bent/broken by the test apparatus of the present invention.

FIG. 6 shows a sample of temperature measurements taken in association with the test apparatus of the present invention.

FIG. 7 shows material testing device used in a laboratory setting to estimate the mechanical work required to bend the copper rods of FIG. 5.

DETAILED DESCRIPTION

FIG. 1 shows an exploded view of one embodiment of an apparatus 10 of the present invention for performing a bending operation on a bar or rod-shaped workpiece using the expansion of H₂O as it transitions from a liquid (water) to a solid (ice).

The apparatus 10 features a hollow cylinder 12 having a main cylindrical bore 14 passing longitudinally therethrough from one end of the cylinder to the other, and a smaller transverse cylindrical bore 16 passing diametrically through the cylinder at a location between the two ends thereof. The cylinder 12 is internally threaded at each end of the main cylindrical bore 14.

A closure piece 18 is selectively engagable to the cylinder 12 at a respective end thereof to close off the main cylindrical bore 14 of the cylinder 12. The closure piece 18 features a plate-like cylindrical cap portion 20 having an outer diameter that exceeds the diameter of the cylinder's main bore, and a smaller diameter cylindrical stem or shaft portion 22 projecting normally from the cap portion 20 to one side thereof. The stem portion 22 is externally threaded in a thread pattern matable with the internal threading at the respective end of the cylinder 12. A closure member o-ring seal 24 is sized to stretch around the stem portion 22 in a sealing manner at a location seated against the cap portion 20 at the face thereof from which the stem projects. Accordingly, the stem 22 of the closure member 18 is initially threaded into the respective end of the cylinder's main bore 14 with the o-ring seal 24 in position at the capped end of the stem 22, and then rotated further in the same threading direction to move the cap 20 toward the respective annular end face of the hollow cylinder 12 to a point sufficiently tight to compress the o-ring 24 between the end of the cylinder and the face of the cap 20. Sealed against the cylinder end and the closure member cap and stem, the o-ring thus acts to ensure a fluid-tight seal at the closure of the respective end of the main cylinder bore by the closure member.

A cover piece 26 is selectively engagable to the other end of the cylinder 12 to lie opposite the closure member 18 and likewise close off the second end of the cylinder's main bore 14. In the illustrated embodiment, the cover piece is identical to the closure member 18, and accordingly threads onto the cylinder via coupling of its externally threaded stem or shaft with the cylinder's internal threading at the respective end of the main cylinder bore. In the illustrated embodiment, the cover piece 26 lacks a respective o-ring, but other embodiments may include such a seal at both ends of the cylinder.

A piston 28 has an outside diameter slightly less than the diameter of the cylinder's main bore 14 so as to slidable along the longitudinal axis of the cylinder when received in the main bore thereof. The piston features a pair of circumferential recesses for receiving a respective pair of o-rings 32 each sized to seal against both the piston and the surrounding wall of the cylinder. The illustrated piston is flat at the end 34 thereof that faces toward the closure member 18, but is conically or frustoconically tapered toward the opposing end 36 so as the give the piston a peaked or pointed configuration at the end that points toward the cover piece 26.

The transverse bore 16 of the cylinder 12 passes diametrically through the main longitudinal bore 14 at an intermediate position between the cylinder ends that locate the transverse bore 16 at a distance from the stem of both the closure member 18 and the cover 26.

Use of the apparatus will now be described with reference to FIGS. 2 and 3, in which the illustrated apparatus differs only in the absence of the cover piece 26 of FIG. 1.

To prepare the apparatus for use, first the closure member 18 is engaged to the cylinder in a manner sealing the main bore 14 thereof closed at the respective end thereof to form a container having a hollow cylindrical interior that is closed at one end. The container is then seated upright on this closed end (i.e. with the closure member 18 forming the bottom of the container). Liquid water 38 is then poured into the hollow cylindrical interior of the container through the open top end of the cylinder, filling the main bore of the cylinder to a level below the elevation of the transverse or cross-bore 16 thereof. The piston 28 is then lowered into the main bore of the cylinder 12 through the open top end until the flat bottom of the piston, or the bottom seal thereof, reaches the top surface level of the water. The amount of water previously added to the cylinder is selected such that the combination of the water level and the piston height/length situates the pointed end 36 of the piston at, or a short distance below, the bottom of the transverse cylinder bore 16.

Preparation of the apparatus is completed by then inserting a longitudinal workpiece 40, such as a metal bar or rod, into the transverse bore 16 of the cylinder 12, so that an intermediate portion of the bar or rod extends diametrically across the main longitudinal bore 14, as shown in FIG. 2.

To perform a bending operation on the workpiece 40, cooling of the liquid water 38 is effected to the freezing point, thereby transforming the column of water into a block of ice 42 over time. The expansion of the water that occurs during its phase transition from liquid to solid can only take place in an upward direction due to the constraints presented by the cylinder wall closing around the cylinder's main bore 14 and the closure member 18 closing off the bottom end of the main cylinder bore 14. Accordingly, the expansion of the water drives the piston 28 upward, forcing the pointed tip 36 thereof up against the workpiece 40 at the central axis of the cylinder's main bore 14. With the force of the water/ice expansion being focused at a small area of the workpiece 40 by the pointed piston 36, the workpiece is bent upward at the center of the cylinder's main bore. Needing only water and a source of freezing temperatures, a workpiece having too rigid a structure for manual bending can be bent at a location where conventional metal-bending tools are lacking, but where seasonal or climatic conditions or cooling equipment (such as a conventional freezer) are present.

Referring again to FIG. 1, the apparatus may feature a plurality of differently shaped pistons from which an owner or operator of the apparatus may select according to the output desired from the operation of the workpiece. For example, the figure shows a second piston 28′ having the same flat bottom face and pair of circumferential recesses, but featuring a shorter taper at the working end of the piston to define a less pronounced point or tip, tending to produce a smaller bend angle in a workpiece than the pointier piston 28. The FIG. 1 apparatus features the cover piece 26 for threading onto the cylinder after adding the water and piston for use as a safety device that will block the piston 28 from ejecting out of the top end of the cylinder should the piston break through the workpiece 40 under the force applied by the expanding water/ice. In the illustrated embodiment, the cover piece 26 lacks an o-ring seal, as the water used to the drive the apparatus is prevented from reaching the cover by the seals between the piston and the surrounding cylinder wall.

Test Apparatus

To test the present invention, a test system consisting of the following main parts was constructed:

1—Thick-wall hollow cylinder:

The selected wall thickness was 30 mm to withstand high pressures. The cylinder was made of stainless steel. The cylinder was to be filled with a suitable volume of water (up to 190-196 cm³) sufficient to give the required force due to expansion based on the experimental experience.

2—Moving piston capable of moving upwards and downwards inside the outer hollow cylinder. This part was also made of stainless steel. The upper portion of this moving part was given the shape of a conical or wedge section to apply the desired mechanical work (bending operation) to the test rod.

3—Rubber O-rings to prevent water leakage.

4—Stress gauge at the upper part of the outer cylinder to measure the internal pressure. Thus, the changes of the internal pressure would be recorded as a function of time. A suitable data acquisition system was to be used.

5—Threaded cover to close the outer cylinder. The cover is equipped with a rubber ring to prevent water leakage.

6—Threaded base to close the bottom of the outer cylinder.

7—Test rod of circular cross-section. The rod was to be fixed at the upper portion of the outer cylinder in a perpendicular position to the longitudinal-axis of the outer cylinder. The rod was fixed through two holes in the wall of the outer cylinder. The rod diameter for the test apparatus may vary from 1 to 18 mm.

8—Thermocouples to measure the internal and external temperatures of the outer cylinder.

The system thus featured a test apparatus consistent with the structure shown in FIG. 1.

A freezer was used to put the system in. The freezer was used to lower the water temperature to the freezing point. Safety precautions were considered in case the experiments went out of control and the volume of ice increases beyond expectations, which could cause the conical/wedge piston to be ejected from the cylinder, possibly causing human injury or physical damage.

Experiments

Using the above described test apparatus, experiments were carried out for metallic rods of different diameters. Stainless-steel rods of diameters 8, 10 and 12 mm were tested, and resulting bent rods are shown in FIG. 4. Also, copper rods were tested, with resulting bent and broken rods shown in FIG. 5. A sample of the recorded temperatures through the process is shown in FIG. 6, in which reference character A denotes temperature measurement within the hollow interior of cylinder at a location between the piston and the cylinder's closed bottom, B denotes temperature measurement at the interior wall surface of the cylinder at a location between the workpiece and the top end of the cylinder, C denotes temperature measurement at the exterior wall surface of the cylinder, and D denotes an ambient temperature measurement within the freezer at a distance outside the cylinder.

Mechanical Efficiency of the Test Apparatus

Let us consider that a weight of water of 175 gm was used to bend a copper rod of 6 mm-diameter in the rate of 0.5 mm/min to reach a total bend radius of 11 mm. The freezing temperature was found to be 1 CC below zero. Thus, the net consumed thermal energy can be calculated as:

Q=M _(w) ×C _(p) ×ΔT _(o)

Q=(175 gm)´(1 cal/gm- ° C.)´(1° C.)=175 Cal.

-   -   Q: consumed thermal heat.     -   M_(w): water mass.     -   C_(p): water specific heat (assumed constant).     -   ΔT_(o): temperature degrees below zero centigrade.

A laboratory device (material testing device), FIG. 7, was used to estimate the mechanical work (W_(m)) required to bend a similar copper rod. The experiments revealed that the required work is 32.6 Joules.

Thus, the system efficiency (h) can be calculated as:

h=W _(m) /Q=32.6×100/(175 Cal.×4.186 Joules/Cal.)=4.5%.

Although, the system efficiency is low, the idea itself finds merit in the successful operation of the test apparatus, where the mechanical work that results from the increase of the water volume was used to bend/break metallic bars (e.g., stainless-steel bars of diameters 8, 10 and 12 mm).

So, if heavy mechanical pieces of equipment (machine tools) conventionally used for bending metal workpieces are not available, the present invention may be utilized to perform mechanical work. This situation may be found in suburban and developing areas.

Other Embodiments

Although described above as useful for bending a metal bar or rod, it will be appreciated that the present invention may be employed for other working operations or other workpiece shapes and materials. For example, if the desired end result is two pieces of material each curving toward one of its ends, it may be desirable to bend an initially straight bar or rod to the point of breakage or fracture into two separate pieces. In another example, instead of a rod or bar inserted into a cylindrical cross-bore, a piece of sheet material may be inserted into a transverse slot for stamping-type operations, such as the formation of a dent/dimple or through-hole.

While the illustrated embodiment uses the cylinder wall at the top boundary of the cross-bore to hold the workpiece against the force applied by the piston, other embodiments may employ other arrangements for supporting a workpiece in a position at least partially overlying the cross-sectional area of the main cylinder bore may be employed, for example at an open end of the cylinder. Also, while the test apparatus is described as employing stainless steel for the container and piston, it will be appreciated that other metals or other non-metal materials of suitable strength for withstanding the pressures applied during the water expansion may alternatively be employed.

Although the apparatus is described above as using water as the working substance, it will be appreciated that other substances known to expand during a phase change could be used in the same manner to drive the piston against a workpiece. Most substances differ from water in that they are more dense as a solid than a liquid, and accordingly the apparatus may perform work during a solid-to-liquid phase change (i.e. during the melting process), provided that the working substance within the cylinder has a sufficiently low melting temperature such that components of the apparatus (the cylinder, closure member, piston, o-rings or other seals, and optional cover) will remain stable and operational throughout the substance melting process.

It will also be appreciated that although the container in which the piston is slidably disposed is described as a cylinder, and illustrated with a cylindrical exterior and cylindrical interior bore, it will be appreciated that the shape of the container's exterior may be varied without detriment to the functionality of the apparatus, and that while the portion of the container's interior space travelled by the piston should be of uniform diameter for smooth travel of the piston and consistent sealing between the piston and surrounding wall, the container need not necessarily be of uniform shape or diameter from the closed bottom end of the container's interior space all the way to the opposing end. Although the illustrated embodiment features a removable closure member at the bottom end of the container, it may instead feature a permanently closed bottom end. However, an openable bottom may have advantages, for example by avoiding a welded-in-place closure, which may produce dangerous thermal stresses.

In the aforementioned tests, the apparatus was disposed within a freezer in order to apply the necessary sub-zero temperatures for freezing the water within the cylinder. FIG. 6 shows the top and bottom ends of the cylinder being recessed into blocks of thermal insulation material 44 so that heat loss from the cylinder is greatest at locations between the two cylinder ends, where the water resides as the working agent or working substance of the apparatus. This way, the cooling effect of the refrigerated space is better focused on the working substance. Similarly, insulating parts of the container located away from the substance to be cooled may be applied where the cooling effect is provided by natural ambient outdoor conditions in colder climates. It will be appreciated that the thermal effect need to change the state of the working substance may be effected by methods other than submersion or placement of the apparatus into controlled or natural environments of suitable temperature. For example, the apparatus may incorporate a dedicated cooling system arranged to cool the interior space of the container.

The illustrated embodiment features a diametric cross-bore as the workpiece support feature and a conically tapering piston as the working member. As a result, the point of contact between the piston and the workpiece is centered on the central longitudional axis of the cylinder bore in which the piston slides. As a result, the piston tends to remain centered in the cylinder bore, minimizing any tilting or side loading of the piston against the cylinder wall. However, through different piston shapes, or different position/orientation of the workpiece support feature, other embodiments may depart from this centering of the engagement point between the piston and workpiece on the central axis of the bore.

Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense. 

1. Apparatus for working of a workpiece, the apparatus comprising: a container comprising a hollow interior space for receipt of a substance known to expand when transitioning from one phase to another; a closure member for closing off a respective end of the hollow interior space of the container in a fluid-tight manner containing the substance within the hollow cylindrical interior space at said respective end; a piston slidable within a cylindrical portion of the hollow interior space of the container along an axis of said hollow interior space; a fluid-tight seal between the piston and a boundary wall closing around the axis of the hollow space for containing the substance within the hollow interior space between the piston and the closure member; and a workpiece support feature arranged to support the workpiece in a position placing at least part of the workpiece over a cross-sectional area of the hollow interior space of the container.
 2. Apparatus for working of a workpiece, the apparatus comprising: a container comprising a hollow interior space containing a substance known to expand when transitioning from one phase to another; a closure member closing off a respective end of the hollow interior space of the container in a fluid-tight manner; a piston slidably disposed within a cylindrical portion of the hollow interior space of the container; a fluid-tight seal between the piston and a boundary wall closing around the axis of the hollow space to contain the substance within the hollow interior space between the fluid-tight seal and the closure member; and a workpiece support feature arranged to support the workpiece in a position placing at least part of the workpiece over a cross-sectional area of the hollow interior space of the container.
 3. The apparatus of claim 1 wherein the workpiece support feature comprises a workpiece passage extending into said container and passing through the hollow interior space thereof at a distance from the closure member for receipt of the workpiece in the passage in a position placing a part of the workpiece within the hollow interior of the container.
 4. The apparatus of claim 2 wherein the workpiece support feature comprises a workpiece passage extending into said container and passing through the hollow interior space on a side of the piston opposite the closure member for receipt of the workpiece in the passage in a position placing part of the workpiece within the hollow interior of the container.
 5. The apparatus of claim 3 wherein the workpiece passage comprises a cylindrical bore.
 6. The apparatus of claim 1 wherein the closure member is removably engagable to the container for selective opening and closing of the respective end of the hollow interior space.
 7. The apparatus of claim 6 wherein the closure member and the container are matingly threaded.
 8. The apparatus of claim 1 wherein a working end of the piston comprises a non-planar surface for working the workpiece.
 9. The apparatus of claim 8 wherein the working end of the piston is at least partially conical.
 10. The apparatus of claim 8 wherein the working end of the piston is wedge-shaped.
 11. The apparatus of claim 1 further comprising a cover for closing off a second end of the hollow interior space.
 12. The apparatus of claim 11 wherein the cover is selectively engagable to and removable from the container.
 13. The apparatus of claim 1 wherein the piston is one of a plurality of differently shaped pistons selectable for use within the hollow interior.
 14. The apparatus of claim 13 wherein each piston comprises a peaked end tapering at a respectively different angle.
 15. The apparatus of claim 2 wherein the substance is one that expands as it transitions into a solid state.
 16. The apparatus of claim 15 wherein the substance is water.
 17. A method of working a workpiece, the method comprising: (a) providing a container comprising a hollow interior space that has at least one closed end and contains a substance known to expand when transitioning from one phase to another; (b) positioning the workpiece in a manner holding at least part of the workpiece over a cross-sectional area of the hollow interior space of the container; and (c) with the substance contained between the closed end of the hollow interior space and a piston slidably disposed within a cylindrical portion of the hollow interior space, causing the substance to transition from the one phase to the other to force the piston against the workpiece to perform a working operation thereon.
 18. The method of claim 17 wherein step (b) comprises inserting the workpiece into a workpiece passage that extends into the container and passes through the hollow interior space thereof on a side of the piston opposite the closure member.
 19. The method of claim 17 wherein step (c) comprises causing the substance to solidify.
 20. The method of claim 17 wherein step (c) comprises cooling the substance. 